...does not need to have a tree view because of the action window...
I totally disagree. Just two quick examples: 1. Using a scroll wheel with a tree view can be very efficient for ad hoc searchs. 2. My wife and neighbors love the tree view for navigation. Some people really have a hard time moving their eyes from location to location. Clicking in the tree and drilling down allows these folks to keep their eyes in one location and then when they find what they're looking for, they're ready to move their eyes again. I know that sounds esoteric, but I've seen it many times.
...and will make different and good looking...
IMO, these are not good enough reasons to dump the tree view for some trumped up tab view mechanism. Give me some examples to think otherwise.
will j.river will include this great feature ?
At the risk of being cliche, beauty is in the eye of the beholder, in other words, the "greatness" of tabbed interfaces, IMO, is subjective. I believe there is a place for tabs in certain applications, but in the case of MC, not at the expense of the tree view or the panes.
Please don't take my reponse the wrong way, I'm not intending to nit-pick your choice of words.